1. Field of the Invention
The present invention relates to a primary battery such as an aluminum negative electrode battery using at least one of aluminum and aluminum alloy as a negative electrode active material.
2. Description of the Related Art
At present, manganese batteries and alkaline batteries are widely used in portable appliances. Manganese batteries and alkaline batteries both comprise negative electrodes made of zinc and positive electrodes containing manganese dioxide, and have an electromotive force of 1.5 V. Owing to recent developments in portable appliances, primary and secondary batteries of high voltage, large capacity, and light weight are being demanded.
For example, a primary battery using aluminum as its negative electrode is expected to have high voltage, large capacity, and light weight compared with a primary battery using zinc as its negative electrode, and has been researched for a long time. For instance, the specification of U.S. Pat. No. 2,838,591 discloses a battery comprising a positive electrode including manganese dioxide, a negative electrode made of aluminum, and an electrolytic solution made of weak acidic aqueous solution of aluminum chloride. This battery, however, has a problem in reactivity between the aluminum used in the negative electrode and the electrolytic solution, and is hence large in self-discharge, large in generation of hydrogen gas, and small in capacity.
More recently, a highly practicable aluminum negative electrode battery has been proposed as in Jpn. Pat. Appln. KOKAI Publication No. 2001-319662. In this aluminum negative electrode battery, however, even if there is no factor for inducing hydrogen gas generation such as an external short-circuit or abnormal high temperature, the negative electrode and electrolysis solution react with each other to generate a huge quantity of hydrogen gas, and a high discharge capacity cannot be obtained. Aside from the tremendous gas generation during discharge, there is a possibility of electrolyte leakage induced by the osmotic phenomenon caused by dissolution of discharge product of the negative electrode into the electrolysis solution, and it is far from commercial production.
On the other hand, according to Jpn. Pat. Appln. KOKAI Publication No. 8-77996, a water repellent polymer sheet having gas permeable and liquid impermeable properties is provided between the gasket and the negative electrode bottom plate, and the gas in the battery is forced outside the battery, and leakage or scattering of electrolytic solution to the outside of the battery is prevented.
However, the battery disclosed in Jpn. Pat. Appln. KOKAI Publication No. 8-77996 is large in electrolyte leakage, and high discharge capacity cannot be achieved.